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I was contacted recently by Drake to ask if he could boot a bootable DOS ISO from Easy2Boot but hide the E2B drive (which normally appears as the first hard disk (hd0) in the system).

So I have now added support for the file extensions .isonousb and .imgnousb (and .imanousb).

A file with a .isonousb extension should be a DOS-bootable ISO (which can be compressed to .gzip format). E2B will map the ISO file as a CD (device 0xff) and map the E2B USB drive as the first floppy disk (fd0). If the E2B USB drive is formatted as FAT/FAT32 it will therefore be accessible to DOS. The internal hard disks are all remapped: e.g.

Before:

hd0 = E2B USB drive

hd1 = 1st internal hard drive

hd2 = 2nd internal hard drive

fd0 = system floppy (if present)

fd1 = system floppy (if present)

After booting:

hd0 = 1st internal hard drive

hd1 = 2nd internal hard drive

fd0 = E2B USB drive

fd1 = not present

This means that an ISO such as fd11src.iso (the FreeDos v1.1 CD) will not see the USB drive when it is booted (e.g. when running FreeDOS fdisk).

.imgnousb and .imanousb work in a similar way, but the image file will appear as floppy 0 and the E2B USB drive will appear as floppy 1:

Before:

hd0 = E2B USB drive

hd1 = 1st internal hard drive

hd2 = 2nd internal hard drive

fd0 = system floppy (if present)

fd1 = system floppy (if present)

After booting:

hd0 = 1st internal hard drive

hd1 = 2nd internal hard drive

fd0 = image

fd1 = E2B USB drive

This may be useful for DOS floppy images that you want to boot but do not want them to access the USB drive as a hard disk - e.g. PartitionGuru401FreeDos.img.

Note that although the E2B USB drive is mapped as a floppy drive, it will only be accessible to DOS if it is formatted as FAT\FAT16 or FAT32 (not NTFS or ext2/3/4 or exFAT).

Also note that this will only work with payloads that use the BIOS directly (such as FreeDOS, MS-DOS, Win3.11, Win98, etc.). Payloads such as XP, Vista, Win7/8/10 or linux will be able to access the E2B USB drive as a USB device as normal.

The payload file is loaded into memory, so if required, you should be able to remove the E2B USB drive as soon as the payload has booted.

The sample .mnu files DOS_ISOnoUSB.mnu and DOS_IMAnoUSB.mnu in the \_ISO\docs\Sample mnu Files folder can be used if you want to make your own menus.